AbstractWe report on the preparation of (11n) oriented thin films of Bi2Sr2CaCu2O8+x (Bi2212), which were fabricated by the metal-organic decomposition method on SrTiO3 (110) and characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM) measurements. By controlling the post-deposition annealing condition (temperature 640°C ≤ Ta ≤ 780°C and time 30min ≤ ta ≤ 120min), films with only the Bi2212 (117) XRD peak were obtained under the condition Ta = 780°C and ta = 30min. Furthermore, by forming films with a double-layer structure, films are found to have better crystallinity. Film properties are discussed on basis of SEM and resistivity measurements

Atsumi, T.

Ishibashi, T.

Kato, T.

Mori, N.

Yamada, Y.

Elsevier - Publisher Connector 

 Physics Procedia  65 ( 2015 )  165 – 168 
Available online at www.sciencedirect.com
1875-3892 © 2015 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license 
(http://creativecommons.org/licenses/by-nc-nd/4.0/).
Peer-review under responsibility of the ISS 2014 Program Committee
doi: 10.1016/j.phpro.2015.05.100 
ScienceDirect
27th International Symposium on Superconductivity, ISS 2014 
Preparation of (11n) Oriented Bi2Sr2CaCu2O8+x thin films 
by the metal-organic decomposition method 
Y. Yamadaa,*, N. Moria, T. Atsumia, T. Katob, T. Ishibashib 
aNational Institute of Technology, Oyama College, 771 Oaza-Nakakuki, Oyama-shi, 323-0806, Japan 
bNagaoka University of Technology, 1603-1 kamitomioka-machi, Nagaoka-shi, 940-2188, Japan 
Abstract 
We report on the preparation of (11n) oriented thin films of Bi2Sr2CaCu2O8+x (Bi2212), which were fabricated by the metal-organic 
decomposition method on SrTiO3 (110) and characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM) 
measurements. By controlling the post-deposition annealing condition (temperature 640 ºC ≤ Ta ≤ 780 ºC and time 30 min ≤ ta ≤ 120 
min), films with only the Bi2212 (117) XRD peak were obtained under the condition Ta = 780 ºC and ta = 30 min. Furthermore, by 
forming films with a double-layer structure, films are found to have better crystallinity. Film properties are discussed on basis of 
SEM and resistivity measurements. 
© 2015 The Authors. Published by Elsevier B.V. 
Peer-review under responsibility of the ISS 2014 Program Committee. 
Keywords: Bi2212; (11n) oriented; in-plane anisotropy; MOD method; thin films 
1. Introduction 
The oscillator using intrinsic Josephson junctions of Bi2Sr2CaCu2O8+x (Bi2212) is considered to be a promising 
device that fills the frequency domain called the "terahertz gap". It has already been proved that the PW class 
continuous coherent terahertz wave can be oscillated [1]. The major preparation methods thus far reported on the 
Bi2212 intrinsic Josephson junction device require complicated procedures, such as the etching process of c-axis 
oriented Bi2212 thin films in the depth direction. However, if non-c-axis oriented thin films are used, it would be 
possible to prepare the planar type device without the etching in the depth direction. 
The metal-organic decomposition (MOD) method is attractive as one of the useful preparation techniques. It has 
been reported that, using this method, high quality c-axis oriented Bi2212 thin films on SrTiO3 (STO) (100) substrates 
have been prepared by controlling only the post-depositing conditions [2, 3]. It is also expected that the crystal 
orientation is controllable by selecting a suitable substrate [4, 5]. In this study, we report on the preparation of MOD 
Bi2212 thin films with the (11n) orientation using STO (110) substrates, and characterization by measurements of the 
X-ray diffraction (XRD), scanning electron microscopy (SEM) and resistivity measurements. 
 
 
* Corresponding author. Tel.: +81-285-20-2234; fax: +81-285-20-2885. 
E-mail address: yyamada@oyama-ct.ac.jp 
 2015 The Authors. Published by Elsevi r B.V. This is an open access article under the CC BY-NC-ND license 
(http://creativecommons. rg/licenses/by-nc-nd/4. /).
Peer-review under responsibility of the ISS 2014 Program Committee
166   Y. Yamada et al. /  Physics Procedia  65 ( 2015 )  165 – 168 
2. Experimental 
Bi2212 thin films under study were prepared by the MOD method using a stoichiometric Bi-Sr-Ca-Cu-O metal 
organic (MO) solution purchased from Kojundo Chemical Lab. Co., Ltd.. Substrates used are STO (110), the size of 
which is 10 mm × 10 mm × 0.5 mm t. Preparation procedures are as follows [3]: 
(1) 6P" Bi-Sr-Ca-Cu-O MO solution was dropped onto substrates using a digital micropipette. 
(2) The dropped solution was spin-coated by a 2-step process with 500 rpm for 5 sec and 3000 rpm for 1 min. 
(3) The spin-coated films were dried in a thermostat chamber at 120 ºC for 40 min. 
(4) The films were annealed in a box furnace at a fixed temperature Ta for an annealing time ta in O2 atmosphere. 
The annealing started at Ta directly and cooling was carried out naturally. When depositing the second layer of the 
thin film, the above steps are repeated. The crystal structures of the annealed thin films were investigated by XRD 
measurements. The surface morphologies were observed by SEM. The resistive transition (RT) curves were measured 
using the dc four-terminal method in a cryostat. Summary of sample labels and their annealing conditions is shown in 
Table 1. Sample S780c2 only has a double-layer structure, while the others have single-layer structures. 
Table 1. Summary of sample labels and their annealing conditions. *1 and *2 represent conditions in the bottom layer and the top layer, respectively. 
Sample label Annealing temperature Ta [ºC] Annealing time ta [min] 
S640a 640 120 
S690a 690 120 
S720a 720 120 
S750a 750 120 
S780a 780 120 
S780b 780 60 
S780c 780 30 
S780c2 
780 *1 30 *1 
810 *2 120 *2 
 
3. Results and discussion 
3.1. XRD patterns 
Figures 1 (a) and (b) show a comparison of the XRD patterns in our samples with different annealing temperatures Ta 
= 690 ºC and 780 ºC for a fixed annealing time ta = 120 min. The diffraction peak of Bi2Sr2CuO6+x (Bi2201) (115) is 
observed at 2T = 29.8º as indicated by asterisk (*), which is commonly observed in samples with 640 ºC ≤ Ta ≤ 750 ºC. 
On the other hand, when the annealing was carried out at Ta = 780 ºC, the diffraction peak of Bi2212 (117) appears at 
2T = 31.0º as indicated by open circle (○), no such peak being observed in samples prepared under the annealing 
conditions 640 ºC ≤ Ta ≤ 750 ºC and ta = 120 min. It is found that the intensity of Bi2201 (115) peak tends to vanish 
with decreasing ta as displayed in Fig. 1 (c) for the sample S780c. Therefore, the condition Ta = 780 ºC for ta = 30 min is 
most preferable among the annealing processes listed in Table 1. By adopting the double-layer structure, we have 
eventually obtained samples showing no evidence of the Bi2201 (115) XRD peak, a typical data of which are displayed 
in Fig. 1 (d). 
 
 
Fig. 1. XRD patterns of samples (a) S690a, (b) S780a, (c) S780c and (d) S780c2. The open circles (○) and asterisks (*) indicate the diffraction peaks 
of Bi2201 (115) and Bi2212 (117), respectively. 
 Y. Yamada et al. /  Physics Procedia  65 ( 2015 )  165 – 168 167
3.2. SEM images 
Figure 2 shows SEM images (x15000) of samples (a) S780c and (b) S780c2. The arrows in Figs. 2 (a) and (b) 
represent the Bi2212 [1ͳത0] direction. Crystal grains with stripe-like structures can be observed in both of the samples. 
The grains with such structures exist only partially in Fig. 2 (a), whereas those are grown over the entire region of Fig. 2 
(b). Judging from the results for XRD patterns, these crystal grain structures are regarded as being the Bi2212 (117) 
orientation. According to Refs. [4] and [5], Bi2212 [1ͳത0] direction is assumed to be the direction of the stripe-like 
structure. A top view of the lattice matching for Bi2212 (117) and STO (110) substrate planes is illustrated in Fig. 2 (c). 
The lattice constants of Bi2212 are assumed to be a = b = 5.4 Å, c = 30.8 Å, and those of STO are assumed to be a = b 
= c = 3.9 Å, respectively. Therefore, mismatch in the lattice constant of Bi2212 (117) with respect to the substrate is 
2.2% for the STO [001] direction of the substrate and that for the STO [ͳത10] direction is + 5.6%. In Fig. 2 (d) we 
show a side view of Bi2212 crystals from the Bi2212 [1ͳത0] direction, from which the c-axis of Bi2212 is regarded to be 
inclined by approximately 49º from the normal direction of substrate. The c-axis of Bi2212 is perpendicular to the STO 
[001] direction, and this structure is considered to form a random twin structure. 
 
           
    
Fig. 2. SEM images (x15000) of surface morphology of samples (a) S780c and (b) S780c2. The arrows along the stripe-like structures indicate the 
direction of Bi2212 [1ͳത0], which is along STO [001]. (c) Schematic drawing of a top view of the lattice matching for Bi2212 (117) and STO (110) 
substrate planes. (d) Schematic drawing of a side view of the Bi2212 unit cell from the [1ͳത0] direction. 
 
3.3. RT curves 
For the representation of RT data, we use the sheet resistance rather than the resistivity since the dimensions of the 
sample area where the measuring current flows is not exactly known. Figure 3 shows RT curves measured (a) along the 
Bi2212 [1ͳത0] direction shown in Fig. 2 (b) for which the sheet resistance is referred to as ܴ௦௔  and (b) along its 
perpendicular direction as ܴ௦௕. Room-temperature values of the sheet resistance in sample S780c2 are ܴ௦௔ ൌ ͲǤʹ͹ȳȀǤ, 
and ܴ௦௕ ൌ ͻͳͲȳȀǤ. The large difference in these resistance values is originated from the stripe-like structure of the 
film. The RT data in Fig. 3 (a) show a double transition behavior with the resistance drops at about T = 80 K and 40 K, 
between which the RT exhibits a semiconducting feature. The reason of this strange variation would be deduced that the 
film is composed of metallic grains with semiconducting grain boundaries. On the other hand, the RT data in Fig. 3 (b) 
shows a monotonous transition, which is considered that ab-plane of adjacent crystal grains are connected by grain 
boundaries, because it forms the twin structure. Furthermore, since the lattice mismatch is large, it is considered that the 
crystal grains with each other are connected only partially, and as a result resistance is much larger. 
 
Bi2212 [1ͳത0] 
1 Pm 
(a) (b) 
Bi2212 [ͳͳത0] 
1 Pm 
168   Y. Yamada et al. /  Physics Procedia  65 ( 2015 )  165 – 168 
 
Fig. 3. RT curves of (a) along the Bi2212 [1ͳത0] direction and (b) along perpendicular direction of Bi2212 [1ͳത0]. 
 
4. Conclusion 
A trial study has been presented for fabricating Bi2212 films with (11n) orientation, using the conventional MOD 
method. By changing annealing conditions, films with Bi2212 (117) orientation have been obtained under the 
conditions Ta = 780 ºC and ta = 30 min. The crystalline properties are found to be improved by the deposition of another 
MOD layer forming a double-structure. The SEM study has been used to characterize the film morphology, 
demonstrating a stripe-like structure. The resistive data may lend support to the existence of the stripe-like structure. 
Acknowledgements 
This study was partly supported by Grant-in-Aid for Cooperative Education and Research among Nagaoka 
University of Technology and National Institute of Technology, Oyama College. 
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[3] Y. Deguchi, H. Kikuchi, N. Mori, Y. Yamada, T. Atsumi, K. Yoshida, T. Ishibashi, Physics Procedia 45 (2013) 193-196 
[4] K. Kuroda, K. Kojima, O. Wada, M. Tanioku, K. Yokoyama, K. Hamanaka, Jpn. J. Appl. Phys. 29 (1990) L1816-L1818 
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Preparation of (11n) Oriented Bi2Sr2CaCu2O8+x Thin Films by the Metal-organic Decomposition Method 

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Preparation of (11n) Oriented Bi2Sr2CaCu2O8+x Thin Films by the Metal-organic Decomposition Method

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